Image pickup lens for solid-state image pickup element

ABSTRACT

Disclosed is a low-cost, compact image pickup lens for a solid-state image pickup element. The image pickup lens includes, in the order from an object side, a first lens L 1 , which has a convex surface facing the object side on an optical axis and has a positive refractive power; a second lens L 2 , which has a concave surface facing an image side on the optical axis and has a negative refractive power; a third lens L 3 , which has a convex surface facing the object side on the optical axis and has a meniscus shape; a fourth lens L 4 , which has a convex surface facing the image side on the optical axis, has a positive refractive power, and has a meniscus shape; and a fifth lens L 5 , which has a concave surface facing the image side on the optical axis, has a negative refractive power, and has a meniscus shape.

This application is a reissue continuation of application Ser. No.14/993,854, which is a reissue continuation of application Ser. No.14/684,878 and an application for reissue of U.S. Pat. No. 8,422,145,and application Ser. No. 14/684,878 is an application for reissue ofU.S. Pat. No. 8,422,145; more than one reissue of U.S. Pat. No.8,422,145 has been filed, including application Ser. No. 14/993,878,filed Jan. 12, 2016, which is a reissue continuation of application Ser.No. 14/684,878, application Ser. No. 15/604,961, filed May 25, 2017,which is a reissue continuation of application Ser. No. 14/993,854,application Ser. No. 15/604,998, filed May 25, 2017, which is a reissuecontinuation of application Ser. No. 14/993,854, application Ser. No.15/605,034, filed May 25, 2017, which is a reissue continuation ofapplication Ser. No. 14/993,854.

TECHNICAL FIELD

The present invention relates to an image pickup lens for a solid-stateimage pickup element that is used in a small-size image pickup devicefor mobile terminals, PDA (Personal Digital Assistance) devices, andother small-size, thin electronic devices.

BACKGROUND ART

In recent years, the market for mobile terminals having an image pickupdevice has grown. Consequently, the image pickup device has begun toincorporate a small-size, high-pixel-number, solid-state image pickupelement.

As an increasing number of small-size, high-pixel-number, image pickupelements are used, it is demanded that image pickup lenses be improvedin terms of resolution and image quality. It is also demanded that suchhigh-resolution, high-quality image pickup lenses become widespread andavailable at low cost.

An image pickup lens having plural lenses is made commonly available tomeet the demand for high performance. An image pickup lens having fivelenses, which exhibit higher performance than a lens having two to fourlenses, is also proposed.

An image pickup lens disclosed, for instance, in Patent Document 1exhibits high performance by including, in the order from an objectside, a first lens, a second lens, a third lens, a fourth lens, and afifth lens. The first lens has a convex surface on the object side andhas a positive refractive power. The second lens has a concave surfacefacing an image side, has a negative refractive power, and has ameniscus shape. The third lens has a convex surface facing the imageside, has a positive refractive power, and has a meniscus shape. Thefourth lens has an aspherical surface on both sides, has a concavesurface on the image side on an optical axis, and has a negativerefractive power. The fifth lens has an aspherical surface on both sidesand has a positive or negative refractive power.

An image pickup lens disclosed, for instance, in Patent Document 2exhibits high performance by including, in the order from an objectside, a first lens, a second lens, a third lens, a fourth lens, and afifth lens. The first lens has an aperture stop and has a positiverefractive power. The second lens is joined to the first lens and has anegative refractive power. The third lens has a concave surface facingthe object side and has a meniscus shape. The fourth lens has a concavesurface facing the object side and has a meniscus shape. The fifth lenshas at least one aspherical surface, has a convex surface facing theobject side, and has a meniscus shape.

CITATION LIST Patent Documents

-   Patent Document 1: JP-A No. 2007-264180-   Patent Document 2: JP-A No. 2007-298572

SUMMARY OF INVENTION Problems to be Solved by the Invention

The image pickup lenses described in Patent Documents 1 and 2 eachinclude five lenses to exhibit high performance. From the viewpoint oftheir optical length, however, they are not adequately designed toreduce their size and thickness.

The present invention has been made in view of the above circumstancesand has an object to provide a small-size, low-cost, high-performanceimage pickup lens for a solid-state image pickup element.

Means for Solving the Problems

The above-mentioned problem can be addressed when the image pickup lensfor a solid-state image pickup element is configured as described below.

The image pickup lens described in aspect 1 of the invention includes,in the order from an object side, a first lens, a second lens, a thirdlens, a fourth lens, and a fifth lens. The first lens has a convexsurface facing the object side on an optical axis and has a positiverefractive power. The second lens has a concave surface facing an imageside on the optical axis and has a negative refractive power. The thirdlens has a convex strike facing the object side on the optical axis andhas a meniscus shape. The fourth lens has a convex surface facing theimage side on the optical axis, has a positive refractive power, and hasa meniscus shape. The fifth lens has a concave surface facing the imageside on the optical axis, has a negative refractive power, and has ameniscus shape.

The image pickup lens described in aspect 2 of the invention satisfiesconditional expressions (1) and (2) below, which concern the Abbe numberof a material used for the first lens and the second lens:45<ν1<90  (1)22<ν2<35  (2)where ν1 is the Abbe number for d-line of the first lens, and ν2 is theAbbe number for d-line of the second lens.

Conditional expression (1) above defines the Abbe number of the firstlens. If the lower limit indicated by conditional expression (1) isexceeded, the variance value difference from the second lens isdecreased so that chromatic aberration correction is insufficient. If,on the contrary, the upper limit is exceeded, the balance between axialchromatic aberration and chromatic aberration of magnification isimpaired so that performance deterioration occurs at the periphery of animage area.

Conditional expression (2) above defines the Abbe number of the secondlens. If the lower limit indicated by conditional expression (2) isexceeded, the balance between axial chromatic aberration and off-axischromatic aberration is impaired so that performance deteriorationoccurs at the periphery of the image area. If, on the contrary, theupper limit is exceeded, the variance value difference from the firstlens is decreased so that chromatic aberration correction isinsufficient.

The image pickup lens described in aspect 3 of the invention isconfigured so that the second lens, the third lens, the fourth lens, andthe fifth lens are so-called plastic lenses that have at least oneaspherical surface and are made of a resin material.

Cost reduction can be achieved when at least the second lens, the thirdlens, the fourth lens, and the fifth lens are made of an inexpensiveresin material exhibiting high production efficiency.

The image pickup lens described in aspect 4 of the invention isconfigured so that an aperture stop is positioned on the object side ofthe first lens.

As the aperture stop is positioned on the object side of the first lens,it is easy to reduce a CRA (Chief Ray Angle) and obtain sufficient lightintensity at the periphery of an image surface at which light intensitydecreases.

The image pickup lens described in aspect 5 of the invention isconfigured so that the object-side surface and image-side surface of thefifth lens have an aspherical shape, which contains at least oneinflection point between the center and the periphery of the lens.

As the object-side surface and image-side surface of the fifth lens havean aspherical shape that contains at least one inflection point betweenthe center and the periphery of the lens, it is possible to obtainadequate off-axis performance and CRA.

The image pickup lens described in aspect 6 of the invention isconfigured so that the first lens and the second lens satisfyconditional expressions (3) and (4) below:0.50<f1/f<1.00  (3)−1.50<f2/f<−0.65  (4)

where f is the composite focal length of lenses included in the entireimage pickup lens, f1 is the focal length of the first lens, and f2 isthe focal length of the second lens.

Conditional expression (3) above defines the range of the focal lengthof the first lens with respect to the focal length of the entire imagepickup lens. If the lower limit indicated by conditional expression (3)is exceeded, the focal length of the first lens is too small. This makesit difficult to correct spherical aberration and coma aberration. If, onthe contrary, the upper limit is exceeded, the optical length is toogreat so that the thickness of the image pickup lens cannot besufficiently reduced.

Conditional expression (4) above defines the range of the focal lengthof the second lens with respect to the focal length of the entire imagepickup lens. If the lower limit indicated by conditional expression (4)is exceeded, the power of the second lens is insufficient so thatchromatic aberration cannot be adequately corrected. If, on thecontrary, the upper limit is exceeded, the focal length of the secondlens is too small. This not only makes it difficult to correct sphericalaberration and coma aberration, but also decreases manufacturing errorsensitivity.

The image pickup lens described in aspect 7 of the invention isconfigured so that the fourth lens and the fifth lens satisfyconditional expressions (5) and (6) below:0.9<f4/f<1.50  (5)−1.70<f5/f<−0.85  (6)where f is the composite focal length of lenses included in the entireimage pickup lens, f4 is the focal length of the fourth lens, and f5 isthe focal length of the fifth lens.

Conditional expression (5) above defines the range of the focal lengthof the fourth lens with respect to the focal length of the entire imagepickup lens. If the lower limit indicated by conditional expression (5)is exceeded, the focal length of the fourth lens is too small. Thismakes it difficult to correct astigmatism and coma aberration, anddecreases the manufacturing error sensitivity. If, on the contrary, theupper limit is exceeded, chromatic aberration of magnification andastigmatism are not adequately corrected so that expected performance isnot obtained.

Conditional expression (6) above defines the range of the focal lengthof the fifth lens With respect to the focal length of the entire imagepickup lens. If the lower limit indicated by conditional expression (6)is exceeded, the power of the fifth lens is insufficient. This makes itdifficult to decrease the optical length. If, on the contrary, the upperlimit is exceeded, it is difficult to decrease the CRA, therebydecreasing the manufacturing error sensitivity at low image height.

The image pickup lens described in aspect 8 of the invention isconfigured so that the first lens and the third lens satisfy conditionalexpression (7) below:-0.15<f1/f3<0.37  (7)where f1 is the focal length of the first lens, and f3 is the focallength of the third lens.

Conditional expression (7) above defines the ratio between the focallength of the first lens and the focal length of the third lens. If thelower limit indicated by conditional expression (7) is exceeded, thefocal length of the third lens is negative and too small. This makes itdifficult to provide aberration correction. If, on the contrary, theupper limit is exceeded, the focal length of the third lens is positiveand too small. This impairs the balance between astigmatism and comaaberration and decreases the manufacturing error sensitivity.

The image pickup lens described in aspect 9 of the invention isconfigured so that the second lens, the third lens, and the fourth lenssatisfy conditional expression (8) below:0.0<f2·3·4  (8)where f2·3·4 is the composite focal length of the second, third, andfourth lenses.

Conditional expression (8) above defines the composite focal length ofthe second, third, and fourth lens. If the lower limit indicated byconditional expression (8) is exceeded, the negative power of the secondlens is too strong so that the manufacturing error sensitivity isexcessively low, or the positive power of the fourth lens is too weak sothat it is difficult to correct astigmatism and distortion.

The image pickup lens described in aspect 10 of the invention isconfigured so that the first lens, the second lens, the third lens, thefourth lens, and the fifth lens satisfy conditional expressions (9),(10), and (11) below:f1<|f2|<|f3|  (9)f1<f4<|f3|  (10)f1<|f5|<|f3|  (11)where f1 is the focal length of the first lens, f2 is the focal lengthof the second lens, f3 is the focal length of the third lens, f4 is thefocal length of the fourth lens, and f5 is the focal length of the fifthlens.

Conditional expression (9) above defines the power relationship, thatis, the focal length relationship, between the first lens, the secondlens, and the third lens. If the lower limit indicated by conditionalexpression (9) is exceeded, the negative power of the second lens is toostrong. This increases the optical length and decreases themanufacturing error sensitivity. If, on the contrary, the upper limit isexceeded, the power of the third lens is too strong so that it isdifficult to obtain adequate off-axis performance.

Conditional expression (10) above defines the power relationship, thatis, the focal length relationship, between the first lens, the thirdlens, and the fourth lens. If the lower limit indicated by conditionalexpression (10) is exceeded, the power of the fourth lens is too strong.This increases the optical length and makes it difficult to correctastigmatism and distortion. If, on the contrary, the upper limit isexceeded, the power of the third lens is too strong so that it isdifficult to obtain adequate off-axis performance.

Conditional expression (11) above defines the power relationship, thatis, the focal length relationship, between the first lens, the thirdlens, and the fifth lens. If the lower limit indicated by conditionalexpression (11) is exceeded, the negative power of the fifth lens is toostrong. This makes it difficult to correct coma aberration andastigmatism. If, on the contrary, the upper limit is exceeded, the powerof the third lens is too strong so that it is difficult to obtainadequate off-axis performance.

The third lens has a weaker power than the other lenses. However, itsfront and rear aspherical surfaces effectively work to reduce anaberration caused within the second lens. Particularly, its fourth-orderaspherical coefficient effectively works and plays an important role toexhibit performance characteristics specific to a combination of fivelenses.

The image pickup lens described in aspect 11 of the invention isconfigured so that the curvature radius of the first lens satisfiesconditional expression (12) below:-0.40<r1/r2<0.10  (12)where r1 is the curvature radius of the object-side surface of the firstlens, and r2 is the curvature radius of the image-side surface of thefirst lens.

Conditional expression (12) above defines the lens shape of the firstlens. If the lower limit indicated by conditional expression (12) isexceeded, the optical length cannot be readily reduced. In addition, theerror sensitivity prevailing during the manufacture of the first lensbecomes low. If, on the contrary, the upper limit is exceeded, it isdifficult to maintain a proper aberration balance so that expectedperformance is not obtained.

The image pickup lens described in aspect 12 of the invention isconfigured so that the curvature radius of the fourth lens satisfiesconditional expression (13) below:1.4<r7/r8<3.0  (13)where r7 is the curvature radius of the object-side surface of thefourth lens, and r8 is the curvature radius of the image-side surface ofthe fourth lens.

Conditional expression (13) above defines the lens shape of the fourthlens. If the lower limit indicated by conditional expression (13) isexceeded, the power of the fourth lens is too weak. Consequently,performance deterioration occurs because it is difficult to correctvarious aberrations. If, on the contrary, the upper limit is exceeded,the fourth lens has an excessively strong power or has a small degree ofmeniscus curvature. In this instance, too, it is difficult to maintain aproper aberration balance so that expected performance is not obtained.

The image pickup lens described in aspect 13 of the invention isconfigured so that its image pickup optical system's optical length andfocal length satisfy conditional expression (14) below:1.05<L/f<1.30  (14)where L is the distance between the front surface of the first lens andthe image surface, and f is the composite focal length of lensesincluded in the entire image pickup lens.

Conditional expression (14) above defines the optical length withrespect to the focal length. If the lower limit indicated by conditionalexpression (14) is exceeded, it is difficult to correct variousaberrations due to an excessively decreased optical length. In addition,the manufacturing error sensitivity becomes excessively low. If, on thecontrary, the upper limit is exceeded, it is difficult to reduce thethickness of the image pickup lens due to an excessively increasedoptical length.

The image pickup lens described in claim 14 of the invention isconfigured so that the diameter of the aperture stop satisfiesconditional expression (15) below:0.30<CA1/f<0.50  (15)where CA1 is the diameter of the aperture stop, and f is the compositefocal length of lenses included in the entire image pickup lens.

Conditional expression (15) above defines the F-number (Fno), which isan indication of lens brightness. If the lower limit indicated byconditional expression (15) is exceeded, the F-number is excessivelygreat so that requested brightness is not achieved in most cases. If, onthe contrary, the upper limit is exceeded, the F-number is excessivelysmall or the distance between an aperture stop (F-number light fluxrestriction plate) and the front surface of the first lens isexcessively great. In either of these cases, expected opticalperformance is not obtained.

Effects of the Invention

The image pickup lens according to the present invention includes fivelenses (the first to fifth lenses). Further, the third lens plays a rolethat is not found in a conventional four-lens configuration. Therefore,the present invention makes it possible to provide a high-performance,low-cost, compact lens in which various aberrations are properlycorrected to support large-size, high-resolution image pickup elementshaving highly minute pixels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an image pickup lens according to afirst embodiment of the present invention.

FIG. 2 shows various aberrations of the image pickup lens according tothe first embodiment of the present invention.

FIG. 3 is a cross-sectional view of the image pickup lens according to asecond embodiment of the present invention.

FIG. 4 shows various aberrations of the image pickup lens according tothe second embodiment of the present invention.

FIG. 5 is a cross-sectional view of the image pickup lens according to athird embodiment of the present invention.

FIG. 6 shows various aberrations of the image pickup lens according tothe third embodiment of the present invention.

FIG. 7 is a cross-sectional view of the image pickup lens according to afourth embodiment of the present invention.

FIG. 8 shows various aberrations of the image pickup lens according tothe fourth embodiment of the present invention.

FIG. 9 is a cross-sectional view of the image pickup lens according to afifth embodiment of the present invention.

FIG. 10 shows various aberrations of the image pickup lens according tothe fifth embodiment of the present invention.

FIG. 11 is a cross-sectional view of the image pickup lens according toa sixth embodiment of the present invention.

FIG. 12 shows various aberrations of the image pickup lens according tothe sixth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described by usingconcrete numerical values. In the first to sixth embodiments, the imagepickup lens for a solid-state image pickup element includes, in theorder from the object side, an aperture stop S, a first lens L1, asecond lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, aplane-parallel glass plate IR, and an image surface.

In the first to sixth embodiments, the second lens L2, the third lensL3, the fourth lens L4, and the fifth lens L5 are so-called plasticlenses that have at least one aspherical surface and are made of a resinmaterial. It should also be noted that the aperture stop S is positionedon the object side of the first lens L1.

The object-side surface and image-side surface of the fifth lens L5 havean aspherical shape that contains at least one inflection point betweenthe center and the periphery of the lens. The aspherical shape in eachembodiment is expressed by the following aspherical surface formula inwhich the vertex of a plane is regarded as the origin, the Z-axis isoriented in the direction of an optical axis, and the height measuredperpendicularly to the optical axis is h:Z=(h2/r)/[1+{1−(1+K)(h2/r2)}½]+A₄h⁴+A₆h⁶+A₈h⁸+ . . .

It should be noted that the following symbols are used in the aboveaspherical surface formula and in the description of each embodiment:

Ai: ith-order aspherical coefficient

r: Curvature radius

K: Conical constant

f: Focal length of the entire image pickup lens

F: F-number

d: On-axis surface spacing

nd: Refractive index of a lens material relative to d-line

ν: Abbe number of a lens material

In the subsequent description, the exponent of 10 (e.g, 4.5×10⁻⁰⁴) isexpressed by using the letter E (e.g., 4.5E-04), and surface numbers forlens data are sequentially assigned so that, for example, theobject-side surface of the first lens L1 is surface 1.

First Embodiment

Table 1 shows numerical data about the image pickup lens according tothe first embodiment. FIG. 1 is a cross-sectional view of the imagepickup lens. FIG. 2 shows various aberrations.

TABLE 1 Surface Number r d n d ν K  1 (S) 2.297 0.550 1.5247 56.26 0.175 2 8384.615 0.411 0  3 −6.170 0.299 1.6142 25.58 2.471  4 8.586 0.242 0 5 2.383 0.481 1.5247 56.26 −7.218  6 3.460 0.658 −1.443  7 −2.320 0.8151.5094 56.00 −0.455  8 −1.502 0.217 −0.645  9 2.288 0.897 1.5094 56.00−3.909 10 1.274 0.714 −3.515 11 ∞ 0.300 1.5168 64.20 12 ∞ 0.635 SurfaceNumber A4 A6 A8 A10 A12 A14 A16  1 (S) −5.423E−3 −2.923E−3 −1.511E−22.424E−3 −1.233E−2 3.275E−3 4.002E−3  2 8.525E−3 −2.136E−2 −1.410E−2−1.071E−2 3.924E−3 0 0  3 1.427E−1 −1.124E−1 5.307E−2 −1.649E−2−1.541E−2 1.183E−2 0  4 9.163E−2 −4.267E−2 9.557E−3 1.336E−2 −1.497E−25.154E−3 0  5 −4.203E−2 −4.711E−3 −2.518E−3 2.523E−3 0 0 0  6 −4.458E−2−3.915E−3 −4.687E−4 4.421E−4 0 0 0  7 5.934E−2 −4.778E−2 2.552E−2−7.375E−3 9.592E−4 0 0  8 2.946E−2 −6.592E−3 −1.052E−3 1.407E−3−1.257E−4 0 0  9 −6.925E−2 1.547E−2 −1.984E−3 4.124E−5 2.050E−5−1.537E−6 −5.993E−9 10 −4.400E−2 1.076E−2 −2.049E−3 2.486E−4 −1.983E−51.014E−6 −2.577E−8 f = 4.815 F = 2.8

Second Embodiment

Table 2 shows numerical data about the image pickup lens according tothe second embodiment. FIG. 3 is a cross-sectional view of the imagepickup lens. FIG. 4 shows various aberrations.

TABLE 2 Surface Number r d n d ν K  1 (S) 2.035 0.605 1.497 81.60 0.145 2 −19.788 0.233 0  3 −4.221 0.295 1.6142 25.58 −1.602  4 13.376 0.341 0 5 3.098 0.486 1.5247 56.26 −11.308  6 4.140 0.731 0.271  7 −2.446 0.8181.5247 56.26 −0.334  8 −1.493 0.239 −0.653  9 3.310 0.855 1.5247 56.26−12.446 10 1.488 0.849 −4.788 11 ∞ 0.300 1.5168 64.20 12 ∞ 0.803 SurfaceNumber A4 A6 A8 A10 A12 A14 A16  1 (S) −7.452E−3 −1.617E−4 −1.335E−24.383E−3 −9.221E−3 4.483E−3 −3.834E−3  2 1.998E−2 −2.240E−2 −1.467E−2−1.152E−2 3.209E−3 0 0  3 1.470E−1 −1.118E−1 5.112E−2 −1.648E−2−1.373E−2 1.325E−2 0  4 9.526E−2 −4.060E−2 1.128E−2 1.414E−2 −1.462E−25.794E−3 0  5 −4.356E−2 −4.909E−3 −2.662E−3 2.513E−3 0 0 0  6 −4.106E−2−3.596E−3 3.640E−7 6.811E−4 0 0 0  7 5.620E−2 −4.763E−2 2.579E−2−7.309E−3 9.426E−4 0 0  8 3.109E−2 −6.202E−3 −9.889E−4 1.388E−3−1.345E−4 0 0  9 −7.078E−2 1.540E−2 −1.993E−3 4.351E−5 2.090E−5 1.538E−6−1.030E−8 10 −4.561E−2 1.071E−2 −2.036E−3 2.488E−4 −1.998E−5 9.963E−7−2.502E−8 f = 5.372 F = 2.8

Third Embodiment

Table 3 shows numerical data about the image pickup lens according tothe third embodiment. FIG. 5 is a cross-sectional view of the imagepickup lens. FIG. 6 shows various aberrations.

TABLE 3 Surface Number r d n d ν K  1 (S) 2.093 0.608 1.5441 56.00 0.123 2 −25.611 0.211 0  3 −4.074 0.307 1.5850 30.00 −1.357  4 11.977 0.336 0 5 3.166 0.478 1.5441 56.00 −11.659  6 4.064 0.731 0.351  7 −2.478 0.7901.5247 56.26 −0.290  8 −1.540 0.274 −0.648  9 3.353 0.859 1.5247 56.26−12.746 10 1.488 0.794 −4.901 11 ∞ 0.300 1.5168 64.20 12 ∞ 0.713 SurfaceNumber A4 A6 A8 A10 A12 A14 A16  1 (S) −8.004E−3 4.932E−5 −1.335E−24.345E−3 −9.202E−3 4.586E−3 −3.708E−3  2 1.747E−2 −2.375E−2 −1.468E−2−1.094E−2 3.436E−3 0 0  3 1.466E−1 −1.114E−1 5.110E−2 −1.663E−2−1.384E−2 1.328E−2 0  4 9.639E−2 −4.030E−2 1.113E−2 1.390E−2 −1.439E−25.879E−3 0  5 −4.371E−2 −5.274E−3 −3.020E−3 2.317E−3 0 0 0  6 −4.084E−2−3.546E−3 −2.715E−5 7.200E−4 0 0 0  7 5.558E−2 −4.774E−2 2.575E−2−7.317E−3 9.431E−4 0 0  8 3.087E−2 −6.449E−3 −1.021E−3 1.386E−3−1.344E−4 0 0  9 −7.043E−2 1.531E−2 −2.006E−3 4.195E−5 2.091E−5−1.493E−6 8.400E−10 10 −4.574E−2 1.069E−2 −2.047E−3 2.484E−4 −1.994E−51.002E−6 −2.527E−8 f = 5.269 F = 2.8

Fourth Embodiment

Table 4 shows numerical data about the image pickup lens according tothe fourth embodiment. FIG. 7 is a cross-sectional view of the imagepickup lens. FIG. 8 shows various aberrations.

TABLE 4 Surface Number r d n d ν K  1 (S) 2.119 0.626 1.5441 56.00 0.177 2 −11.544 0.208 0  3 −3.147 0.298 1.5850 30.00 −5.094  4 9.796 0.373 0 5 2.701 0.428 1.5441 56.00 −11.168  6 3.842 0.837 0.129  7 −2.253 0.7501.5247 56.26 −0.654  8 −1.467 0.401 −0.694  9 1.656 0.587 1.5247 56.26−10.501 10 0.981 0.874 −4.578 11 ∞ 0.300 1.5168 64.20 12 ∞ 0.742 SurfaceNumber A4 A6 A8 A10 A12 A14 A16  1 (S) −7.510E−3 1.743E−3 −1.246E−25.493E−3 −8.377E−3 4.978E−3 −3.500E−3  2 2.507E−2 −1.481E−2 −1.129E−2−1.181E−2 3.172E−3 0 0  3 1.526E−1 −1.113E−1 5.074E−2 −1.533E−2−1.395E−2 1.133E−2 0  4 9.710E−2 −4.050E−2 1.124E−2 1.365E−2 −1.474E−25.407E−3 0  5 −3.599E−2 −8.738E−3 −4.179E−3 2.048E−3 0 0 0  6 −4.051E−2−4.801E−3 −6.520E−4 5.650E−4 0 0 0  7 6.564E−2 −4.702E−2 2.607E−2−7.359E−3 8.648E−4 0 0  8 3.490E−2 −3.356E−3 −1.098E−3 1.296E−3−1.421E−4 0 0  9 −7.077E−2 1.589E−2 −1.963E−3 4.145E−5 2.045E−5−1.557E−6 −2.866E−9 10 −5.003E−2 1.088E−2 −1.968E−3 2.477E−4 −2.068E−59.622E−7 −1.548E−8 f = 5.187 F = 2.7

Fifth Embodiment

Table 5 shows numerical data about the image pickup lens according tothe fifth embodiment. FIG. 9 is a cross-sectional view of the imagepickup lens. FIG. 10 shows various aberrations.

TABLE 5 Surface Number r d n d ν K  1 (S) 1.974 0.720 1.5311 56.00 0.260 2 −14.375 0.150 0  3 −4.100 0.350 1.6142 25.58 1.248  4 55.800 0.360 0 5 5.600 0.340 1.5311 56.00 −20.645  6 3.868 0.750 1.356  7 −3.010 0.8201.5311 56.00 −0.508  8 −1.634 0.270 −0.656  9 4.156 0.880 1.5311 56.00−29.637 10 1.582 0.830 −5.617 11 ∞ 0.300 1.5168 64.20 12 ∞ 0.770 SurfaceNumber A4 A6 A8 A10 A12 A14 A16  1 (S) −6.011E−3 4.555E−3 −1.140E−25.896E−3 −7.660E−3 5.633E−3 −3.706E−3  2 3.346E−2 −2.148E−2 −1.342E−2−1.061E−2 3.525E−3 0 0  3 1.407E−1 −1.057E−1 4.976E−2 −1.790E−2−1.431E−2 1.182E−2 0  4 1.000E−1 −4.704E−2 1.326E−2 1.542E−2 −1.468E−25.766E−3 0  5 −5.387E−2 −6.340E−3 −1.971E−3 2.628E−3 0 0 0  6 −4.023E−22.476E−4 1.005E−3 6.170E−4 0 0 0  7 5.679E−2 −4.556E−2 2.594E−2−7.443E−3 8.944E−4 0 0  8 3.073E−2 −5.791E−3 −8.590E−4 1.367E−3−1.517E−4 0 0  9 −6.996E−2 1.530E−2 −1.966E−3 5.619E−5 2.207E−5−1.613E−6 −4.417E−8 10 −4.594E−2 1.064E−2 −2.039E−3 2.506E−4 −2.003E−59.526E−7 −2.202E−8 f = 5.700 F = 2.8

Sixth Embodiment

Table 6 shows numerical data about the image pickup according to thesixth embodiment. FIG. 11 is a cross-sectional view of the image pickuplens. FIG. 12 shows various aberrations.

TABLE 6 Surface Number r d n d ν K  1 (S) 2.084 0.604 1.5311 56.00 0.168 2 −21.296 0.222 0  3 −3.958 0.300 1.6142 25.58 −1.423  4 13.768 0.323 0 5 3.075 0.497 1.5311 56.00 −11.809  6 4.139 0.624 0.275  7 −2.412 0.8701.5247 56.26 −0.378  8 −1.484 0.208 −0.649  9 3.407 0.955 1.5247 56.26−5.620 10 1.561 0.802 −4.276 11 ∞ 0.300 1.5168 64.20 12 ∞ 0.674 SurfaceNumber A4 A6 A8 A10 A12 A14 A16  1 (S) −6.789E−3 2.618E−4 −1.386E−23.682E−3 −9.711E−3 4.535E−3 −2.955E−3  2 1.842E−2 −2.358E−2 −1.510E−2−1.166E−2 3.030E−3 0 0  3 1.465E−1 −1.117E−1 5.082E−2 −1.681E−2−1.391E−2 1.334E−2 0  4 9.611E−2 −4.021E−2 1.153E−2 1.421E−2 −1.461E−25.550E−3 0  5 −4.518E−2 −5.504E−3 −2.914E−3 2.385E−3 0 0 0  6 −4.104E−2−3.503E−3 −5.896E−5 6.932E−4 0 0 0  7 5.684E−2 −4.751E−2 2.584E−2−7.290E−3 9.508E−4 0 0  8 3.092E−2 −6.249E−3 −1.018E−3 1.379E−3−1.373E−4 0 0  9 −6.971E−2 1.550E−2 −1.986E−3 4.363E−5 2.079E−5−1.571E−6 −1.765E−8 10 −4.447E−2 1.070E−2 −2.036E−3 2.489E−4 −1.996E−51.000E−6 −2.448E−8 f = 4.986 F = 2.8

Table 7 below relates to the first to sixth embodiments and shows valuesfor conditional expressions (1) to (17) below.

Conditional expression (1) concerns the Abbe number of a material usedfor the first lens L1. Conditional expression (2) concerns the Abbenumber of a material used for the second lens L2.45<ν1<90  Conditional expression (1)22<ν2<35  Conditional expression (2)where ν1 is the Abbe number for d-line of the first lens, and ν2 is theAbbe number for d-line of the second lens.

Conditional expression (3) defines the range of the focal length of thefirst lens L1 with respect to the focal length of the entire imagepickup lens. Conditional expression (4) defines the range of the focallength of the second lens L2 with respect to the focal length of theentire image pickup lens.0.5<f1/f<1.00  Conditional expression (3)−1.50<f2/f<−0.65  Conditional expression (4)where f is the composite focal length of lenses included in the entireimage pickup lens, f1 is the focal length of the first lens, and f2 isthe focal length of the second lens.

Conditional expression (5) defines the range of the focal length of thefourth lens L4 with respect to the focal length of the entire imagepickup lens. Conditional expression (6) defines the range of the focallength of the fifth lens L5 with respect to the focal length of theentire image pickup lens.0.9<f4/f<1.50  Conditional expression (5)−1.70<f5/f<−0.85  Conditional expression (6)where f is the composite focal length of lenses included in the entireimage pickup lens, f4 is the focal length of the fourth lens, and f5 isthe focal length of the fifth lens.

Conditional expression (7) defines the ratio between the focal length ofthe first lens L1 and the focal length of the third lens L3.−0.15<f1/f3<0.37  Conditional expression (7)where f1 is the focal length of the first lens, and f3 is the focallength of the third lens.

Conditional expression (8) defines the composite focal length of thesecond lens L2, the third lens L3, and the fourth lens L4.0.0<f2·3·4  Conditional expression (8)

Conditional expression (9) defines the power relationship, that is, thefocal length relationship, between the first lens L1, the second lensL2, and the third lens L3. Conditional expression (10) defines the powerrelationship, that is, the focal length relationship, between the firstlens L1, the third lens L3, and the fourth lens L4. Conditionalexpression (11) defines the power relationship, that is, the focallength relationship, between the first lens L1, the third lens L3, andthe fifth lens L5.f1<|f2|<|f3|  Conditional expression (9)f1<f4<|f3|  Conditional expression (10)f1<|f5|<|f3|  Conditional expression (11)

Conditional expression (12) defines the lens shape of the first lens L1.−0.40<r1/r2<0.10  Conditional expression (12)where r1 is the curvature radius of the object-side surface of the firstlens, and r2 is the curvature radius of the image-side surface of thefirst lens.

Conditional expression (13) defines the lens shape of the fourth lensL4.1.4<r7/r8<3.0  Conditional expression (13)where r7 is the curvature radius of the object-side surface of thefourth lens, and r8 is the curvature radius of the image-side surface ofthe fourth lens.

Conditional expression (14) defines the optical length with respect tothe focal length.1.05<L/f<1.30  Conditional expression (14)where L is the distance between the front surface of the first lens andthe image surface, and f is the composite focal length of lensesincluded in the entire image pickup lens.

Conditional expression (15) defines the F-number (Fno), which is anindication of lens brightness.0.30<CA1/f<0.50  Conditional expression (15)where CA1 is the diameter of the aperture stop, and f is the compositefocal length of lenses included in the entire image pickup lens.

Conditional expression (16) defines the range of the focal length of thesecond lens L2 with respect to the focal length of the entire imagepickup lens, and relates to a case where conditions more stringent thanthose defined by conditional expression (4) are satisfied.−1.30<f2/f<−0.75  Conditional expression (16)where f is the composite focal length of lenses included in the entireimage pickup lens, and f2 is the focal length of the second lens.

Conditional expression (17) defines the lens shape of the fourth lens L4and relates to a case where conditions more stringent than those definedby conditional expression (13) are satisfied.1.45<r7/r8<2.0  Conditional expression (17)where r7 is the curvature radius of the object-side surface of thefourth lens, and r8 is the curvature radius of the image-side surface ofthe fourth lens.

TABLE 7 First Second Third Fourth Fifth Sixth Embod- Embod- Embod-Embod- Embod- Embod- iment iment iment iment iment iment Conditional56.26 81.60 56.00 56.00 56.00 56.00 Expression (1) Conditional 25.5825.58 30.00 30.00 25.58 25.58 Expression (2) Conditional 0.909 0.6980.680 0.645 0.582 0.723 Expression (3) Conditional −1.205 −0.966 −0.979−0.778 −1.089 −0.997 Expression (4) Conditional 1.300 1.050 1.141 1.1630.978 1.115 Expression (5) Conditional −1.671 −1.144 −1.150 −1.262−0.957 −1.340 Expression (6) Conditional 0.346 0.185 0.162 0.226 −0.1310.186 Expression (7) Conditional 10.266 10.597 13.323 15.698 18.81610.806 Expression (8) Conditional Expression (9) f 1 4.379 3.747 3.5843.344 3.319 3.606 |f 2| 5.800 5.191 5.160 4.037 6.205 4.973 |f 3| 12.64720.214 22.174 14.764 25.268 19.382 Conditional Expression (10) f 1 4.3793.747 3.584 3.344 3.319 3.606 f 4 6.258 5.638 6.011 6.033 5.577 5.558 |f3| 12.647 20.214 22.174 14.764 25.268 19.382 Conditional Expression (11)f 1 4.379 3.747 3.584 3.344 3.319 3.606 |f 5| 8.045 6.144 6.059 6.5465.457 6.680 |f 3| 12.647 20.214 22.174 14.764 25.268 19.382 Conditional0.000 −0.103 −0.082 −0.184 −0.137 −0.098 Expression (12) Conditional1.545 1.638 1.609 1.536 1.842 1.625 Expression (13) Conditional 1.2921.220 1.215 1.238 1.147 1.279 Expression (14) Conditional 0.357 0.3550.357 0.385 0.355 0.355 Expression (15)

As shown in Table 7, the first to sixth embodiments of the presentinvention satisfy all of conditional expressions (1) to (17).Conditional expressions (1) and (2) define the Abbe number of the firstlens L1 or the second lens L2. If the lower limit indicated byconditional expression (1) or (2) is exceeded, the variance valuedifference from the second lens L2 is decreased so that chromaticaberration correction is insufficient. If, on the contrary, the upperlimit is exceeded, the balance between axial chromatic aberration andchromatic aberration of magnification is impaired so that performancedeterioration occurs at the periphery of the image area. However, whenconditional expressions (1) and (2) are satisfied, a proper balance ismaintained between axial chromatic aberration and chromatic aberrationof magnification. This makes it possible to prevent performancedeterioration at the periphery of the image area and provide excellentchromatic aberration correction.

Conditional expressions (3) and (4) define the range of the focal lengthof the first lens L1 or the second lens L2 with respect to the focallength of the entire image pickup lens. If the lower limit indicated byconditional expression (3) is exceeded, the focal length of the firstlens L1 is too small. This makes it difficult to correct sphericalaberration and coma aberration. If, on the contrary, the upper limit isexceeded, the optical length is too great so that the thickness of theimage pickup lens cannot be sufficiently reduced. If the lower limitindicated by conditional expression (4) is exceeded, the power of thesecond lens L2 is insufficient so that chromatic aberration cannot beadequately corrected. If, on the contrary, the upper limit is exceeded,the focal length of the second lens L2 is too small. This makes itdifficult to correct spherical aberration and coma aberration, anddecreases manufacturing error sensitivity. However, when conditionalexpressions (3) and (4) are satisfied, it is possible to properlycorrect spherical aberration and coma aberration. Further, the power ofthe second lens L2 becomes sufficient, making it possible to properlycorrect chromatic aberration, spherical aberration, and coma aberration.

Conditional expression (5) defines the range of the focal length of thefourth lens L4 with respect to the focal length of the entire imagepickup lens. If the lower limit indicated by conditional expression (5)is exceeded, the focal length of the fourth lens L4 is too small. Thismakes it difficult to correct astigmatism and coma aberration, anddecreases the manufacturing error sensitivity. If, on the contrary, theupper limit is exceeded, chromatic aberration of magnification andastigmatism are not adequately corrected so that expected performance isnot obtained. However, when conditional expression (5) is satisfied, itis easy to correct astigmatism, coma aberration, and chromaticaberration of magnification. This makes it possible to obtain expectedperformance.

Conditional expression (6) defines the range of the focal length of thefifth lens L5 with respect to the focal length of the entire imagepickup lens. If the lower limit indicated by conditional expression (6)is exceeded, the power of the fifth lens L5 is insufficient. This makesit difficult to decrease the optical length. If, on the contrary, theupper limit is exceeded, it is difficult to decrease the CRA, therebydecreasing the manufacturing error sensitivity at low image height.However, when conditional expression (6) is satisfied, the fifth lens L5has a sufficient power, making it possible to reduce the optical length.This makes it easy to decrease the CRA so that the manufacturing errorsensitivity at low image height increases.

Conditional expression (7) defines the ratio between the focal length ofthe first lens L1 and the focal length of the third lens L3. If thelower limit indicated by conditional expression (7) is exceeded, thefocal length of the third lens L3 is negative and too small. This makesit difficult to provide aberration correction. If, on the contrary, theupper limit is exceeded, the focal length of the third lens L3 ispositive and too small. This impairs the balance between astigmatism andcoma aberration and decreases the manufacturing error sensitivity.However, when conditional expression (7) is satisfied, it is easy toprovide aberration correction. Further, it is possible not only toprevent the focal length of the third lens L3 from being positive andtoo small, but also to maintain an excellent balance between astigmatismand coma aberration.

Conditional expression (8) defines the composite focal length of thesecond lens L2, the third lens L3, and the fourth lens L4. If the lowerlimit indicated by conditional expression (8) is exceeded, the negativepower of the second lens L2 is too strong so that the manufacturingerror sensitivity is excessively low, or the positive power of thefourth lens L4 is too weak so that it is difficult to correctastigmatism and distortion. However, when conditional expression (8) issatisfied, it is easy to correct astigmatism and distortion.

Conditional expression (9) defines the power relationship, that is, thefocal length relationship, between the first lens L1, the second lensL2, and the third lens L3. If the lower limit indicated by conditionalexpression (9) is exceeded, the negative power of the second lens L2 istoo strong. This increases the optical length and decreases themanufacturing error sensitivity. If, on the contrary, the upper limit isexceeded, the power of the third lens is too strong so that it isdifficult to obtain adequate off-axis performance. However, whenconditional expression (9) is satisfied, it is possible to decrease theoptical length and easily obtain adequate off-axis performance.

Conditional expression (10) defines the power relationship, that is, thefocal length relationship, between the first lens L1, the third lens L3,and the fourth lens L4. If the lower limit indicated by conditionalexpression (10) is exceeded, the power of the fourth lens L4 is toostrong. This increases the optical length and makes it difficult tocorrect astigmatism and distortion. If, on the contrary, the upper limitis exceeded, the power of the third lens L3 is too strong so that it isdifficult to obtain adequate off-axis performance. However, whenconditional expression (10) is satisfied, it is easy to correctastigmatism and distortion and obtain adequate off-axis performance.

Conditional expression (11) defines the power relationship, that is, thefocal length relationship, between the first lens L1, the third lens L3,and the fifth lens L5. If the lower limit indicated by conditionalexpression (11) is exceeded, the negative power of the fifth lens L5 istoo strong. This makes it difficult to correct coma aberration andastigmatism. If, on the contrary, the upper limit is exceeded, the powerof the third lens L3 is too strong so that it is difficult to obtainadequate off-axis performance. However, when conditional expression (11)is satisfied, it is easy to correct coma aberration and astigmatism andobtain adequate off-axis performance.

Conditional expression (12) defines the lens shape of the first lens L1.If the lower limit indicated by conditional expression (12) is exceeded,the optical length cannot be readily reduced. In addition, the errorsensitivity prevailing during the manufacture of the first lens L1becomes low. If, on the contrary, the upper limit is exceeded, it isdifficult to maintain a proper aberration balance so that expectedperformance is not obtained. However, when conditional expression (12)is satisfied, the optical length can be readily reduced. In addition, itis possible to maintain a proper aberration balance and obtain expectedperformance.

Conditional expression (13) defines the lens shape of the fourth lensL4. If the lower limit indicated by conditional expression (13) isexceeded, the power of the fourth lens L4 is too weak. Consequently,performance deterioration occurs because it is difficult to correctvarious aberrations. If, on the contrary, the upper limit is exceeded,the fourth lens L4 has an excessively strong power or has a small degreeof meniscus curvature. In this instance, too, it is difficult tomaintain a proper aberration balance so that expected performance is notobtained. However, when conditional expression (13) is satisfied, it iseasy to correct various aberrations and maintain a proper aberrationbalance. As a result, expected performance is obtained.

Conditional expression (14) defines the optical length with respect tothe focal length. If the lower limit indicated by conditional expression(14) is exceeded, it is difficult to correct various aberrations due toan excessively decreased optical length. In addition, the manufacturingerror sensitivity becomes excessively low. If, on the contrary, theupper limit is exceeded, it is difficult to reduce the thickness of theimage pickup lens due to an excessively increased optical length.However, when conditional expression (14) is satisfied, it is easy tocorrect various aberrations. In addition, the thickness of the imagepickup lens can be readily reduced because the optical length is notexcessively small.

Conditional expression (15) defines the F-number (Fno), which is anindication of lens brightness. If the lower limit indicated byconditional expression (15) is exceeded, the F-number is excessivelygreat so that requested brightness is not achieved in most cases. If, onthe contrary, the upper limit is exceeded, the F-number is excessivelysmall or the distance between the aperture stop (F-number light fluxrestriction plate) and the front surface of the first lens isexcessively great. In either of these cases, expected opticalperformance is not obtained. However, when conditional expression (15)is satisfied, the expected optical performance can be obtained withease.

Further, the second lens L2, the third lens L3, the fourth lens L4, andthe fifth lens L5 are so-called plastic lenses that have at least oneaspherical surface and are made of a resin material. Cost reduction canbe achieved when at least the second lens L2, the third lens L3, thefourth lens L4, and the fifth lens L5 are made of an inexpensive resinmaterial exhibiting high production efficiency.

Furthermore, as the aperture stop S is positioned on the object side ofthe first lens L1 to decrease the CRA (Chief Ray Angle), it is easy toreduce the CRA (Chief Ray Angle) and obtain sufficient light intensityat the periphery of the image surface at which light intensitydecreases.

Moreover, as the object side surface and image side surface of the fifthlens L5 have an aspherical shape that contains at least one inflectionpoint between the center and the periphery of the lens, it is possibleto obtain adequate off-axis performance and CRA.

While the present invention has been described in terms of exemplaryembodiments, it should be understood that the invention is not limitedto those exemplary embodiments. Those skilled in the art will understandthat various changes and modifications can be made within the scope andspirit of the invention.

EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS L1 First lens L2 Secondlens L3 Third lens L4 Fourth lens L5 Fifth lens S Aperture stop

The invention claimed is:
 1. An image pickup lens for a solid-stateimage pickup element, comprising, in the order from an object side: afirst lens, which has a convex surface facing the object side on anoptical axis and has a positive refractive power; a second lens, whichhas a concave surface facing an image side on the optical axis and has anegative refractive power; a third lens, which has a convex surfacefacing the object side on the optical axis and has a meniscus shape; afourth lens, which has a convex surface facing the image side on theoptical axis, has a positive refractive power, and has a meniscus shape;and a fifth lens, which has a concave surface facing the image side onthe optical axis, has a negative refractive power, and has a meniscusshape.
 2. The image pickup lens according to claim 1, wherein the Abbenumber of a material used for the first lens and the second lenssatisfies conditional expressions (1) and (2) below:45<ν1<90  (1)22<ν2<35  (2) where ν1 is the Abbe number for d-line of the first lens,and ν2 is the Abbe number for d-line of the second lens.
 3. The imagepickup lens according to claim 1, wherein the second lens, the thirdlens, the fourth lens, and the fifth lens are so-called plastic lensesthat have at least one aspherical surface and are made of a resinmaterial.
 4. The image pickup lens according to claim 1, wherein anaperture stop is positioned on the object side of the first lens.
 5. Theimage pickup lens according to claim 1, wherein the object-side surfaceand the image-side surface of the fifth lens have an aspherical shapethat contains at least one inflection point between the center and theperiphery of the lens.
 6. The image pickup lens according to claim 1,wherein the first lens and the second lens satisfy conditionalexpressions (3) and (4) below:0.5<f1/f<1.00  (3)-1.50<f2/f<−0.65  (4) where f is the composite focal length of lensesincluded in the entire image pickup lens, f1 is the focal length of thefirst lens, and f2 is the focal length of the second lens.
 7. The imagepickup lens according to claim 1, wherein the fourth lens and the fifthlens satisfy conditional expressions (5) and (6) below:0.9<f4/f<1.50  (5)-1.70<f5/f<−0.85  (6) where f is the composite focal length of lensesincluded in the entire image pickup lens, f4 is the focal length of thefourth lens, and f5 is the focal length of the fifth lens.
 8. The imagepickup lens according to claim 1, wherein the first lens and the thirdlens satisfy conditional expression (7) below:-0.15<f1/f3<0.37  (7) where f1 is the focal length of the first lens,and f3 is the focal length of the third lens.
 9. The image pickup lensaccording to claim 1, wherein the second lens, the third lens, and thefourth lens satisfy conditional expression (8) below:0.0<f2·3·4  (8) where f2·3·4 is the composite focal length of thesecond, third, and fourth lenses.
 10. The image pickup lens according toclaim 1, wherein the first lens, the second lens, the third lens, thefourth lens, and the fifth lens satisfy conditional expressions (9),(10), and (11) below:f1<|f2|<|f3|  (9)f1<f4<|f3|  (10)f1<|f5|<|f3|  (11) where f1 is the focal length of the first lens, f2 isthe focal length of the second lens, f3 is the focal length of the thirdlens, f4 is the focal length of the fourth lens, and f5 is the focallength of the fifth lens.
 11. The image pickup lens according to claim10, wherein the curvature radius of the first lens satisfies conditionalexpression (12) below:-0.40<r1/r2<0.10  (12) where r1 is the curvature radius of theobject-side surface of the first lens, and r2 is the curvature radius ofthe image-side surface of the first lens.
 12. The image pickup lensaccording claim 10, wherein the curvature radius of the fourth lenssatisfies conditional expression (13) below:1.4<r7/r8<3.0  (13) where r7 is the curvature radius of the object-sidesurface of the fourth lens, and r8 is the curvature radius of theimage-side surface of the fourth lens.
 13. The image pickup lensaccording to claim 10, wherein the optical length and focal length of anoptical system thereof satisfy conditional expression, (14) below:1.05<L/f<1.30  (14) where L is the distance between the front surface ofthe first lens and an image surface, and f is the composite focal lengthof lenses included in the entire image pickup lens.
 14. The image pickuplens according to claim 4, wherein the diameter of the aperture stopsatisfies conditional expression (15) below:0.30<CA1/f<0.50  (15) where CA1 is the diameter of the aperture stop,and f is the composite focal length of lenses included in the entireimage pickup lens.
 15. The image pickup lens according to claim 10,wherein the Abbe number of a material used for the first lens and thesecond lens satisfies conditional expressions (1) and (2) below:45<ν1<90  (1)22<ν2<35  (2) where ν1 is the Abbe number for d-line of the first lens,and ν2 is the Abbe number for d-line of the second lens.
 16. The imagepickup lens according to claim 10, wherein the second lens, the thirdlens, the fourth lens, and the fifth lens are so-called plastic lensesthat have at least one aspherical surface and are made of a resinmaterial.
 17. The image pickup lens according to claim 10, wherein anaperture stop is positioned on the object side of the first lens. 18.The image pickup lens according to claim 10, wherein the object-sidesurface and the image-side surface of the fifth lens have an asphericalshape that contains at least one inflection point between the center andthe periphery of the lens.
 19. An image pickup lens for a solid-stateimage pickup element, comprising, in order from an object side: a firstlens, which has a convex surface facing the object side on an opticalaxis and has a positive refractive power; a second lens; a third lens,which has a convex surface facing the object side and has a meniscusshape; a fourth lens, which has a convex surface facing an image side onthe optical axis; and a fifth lens, which has a concave surface facingthe image side on the optical axis and has a negative refractive power,wherein: the second lens, the third lens, the fourth lens, and the fifthlens are plastic lenses that have at least one aspherical surface andare made of a resin material; each of the first lens, the second lens,the third lens, the fourth lens, and the fifth lens is positionedwithout being joined on surfaces facing each other; and the first lensand the second lens satisfy conditional expressions (3) and (4) below:0.5<f1/f<1.00  (3)−1.50<f2/f<−0.65  (4) where f is a composite focal length of lensesincluded in an entirety of the image pickup lens, f1 is a focal lengthof the first lens, and f2 is a focal length of the second lens.
 20. Theimage pickup lens according to claim 19, wherein Abbe numbers ofmaterials used for the first lens and the second lens satisfyconditional expressions (1) and (2) below:45<ν1<90  (1)22<ν2<35  (2) where ν1 is an Abbe number for d-line of the first lens,and ν2 is an Abbe number for d-line of the second lens.
 21. The imagepickup lens according to claim 19, wherein the second lens has a concavesurface facing the image side on the optical axis and has a negativerefractive power.
 22. The image pickup lens according to claim 19,wherein an image-side surface of the fifth lens has an aspherical shapethat contains at least one inflection point between a center and aperiphery of the fifth lens.
 23. The image pickup lens according toclaim 19, wherein the first lens and the third lens satisfy aconditional expression (7) below:−0.15<f1/f3<0.37  (7) where f3 is a focal length of the third lens. 24.An image pickup lens for a solid-state image pickup element, comprising,in order from an object side: a first lens, which has a convex surfacefacing the object side on an optical axis and has a positive refractivepower; a second lens; a third lens; a fourth lens, which has a convexsurface facing an image side on the optical axis; and a fifth lens,which has a concave surface facing the image side on the optical axisand has a negative refractive power, wherein: the object-side surface ofthe fifth lens has an aspherical shape that contains at least oneinflection point between the center and the periphery of the lens; thesecond lens, the third lens, the fourth lens, and the fifth lens areplastic lenses that have at least one aspherical surface and are made ofa resin material; each of the first lens, the second lens, the thirdlens, the fourth lens, and the fifth lens is positioned without beingjoined on surfaces facing each other; and the first lens and the secondlens satisfy conditional expressions (3) and (4) below:0.5<f1/f<1.00  (3)−1.50<f2/f<−0.65  (4) where f is a composite focal length of lensesincluded in an entirety of the image pickup lens, f1 is a focal lengthof the first lens, and f2 is a focal length of the second lens.
 25. Theimage pickup lens according to claim 24, wherein Abbe numbers ofmaterials used for the first lens and the second lens satisfyconditional expressions (1) and (2) below:45<ν1<90  (1)22<ν2<35  (2) where ν1 is an Abbe number for d-line of the first lens,and ν2 is an Abbe number for d-line of the second lens.
 26. The imagepickup lens according to claim 24, wherein the second lens has a concavesurface facing the image side on the optical axis and has a negativerefractive power.
 27. The image pickup lens according to claim 24,wherein the third lens has a convex surface facing the object side onthe optical axis and has a meniscus shape.
 28. The image pickup lensaccording to claim 24, wherein an image-side surface of the fifth lenshas an aspherical shape that contains at least one inflection pointbetween a center and a periphery of the fifth lens.
 29. The image pickuplens according to claim 24, wherein the first lens and the third lenssatisfy a conditional expression (7) below:−0.15<f1/f3<0.37   (7) where f3 is a focal length of the third lens. 30.An image pickup lens for a solid-state image pickup element, comprising,in order from an object side: a first lens, which has a convex surfacefacing the object side on an optical axis and has a positive refractivepower; a second lens, which has a negative refractive power; a thirdlens; a fourth lens, which has a convex surface facing an image side onthe optical axis; and a fifth lens, which has a concave surface facingthe image side on the optical axis and has a negative refractive power,wherein: the second lens, the third lens, the fourth lens, and the fifthlens are plastic lenses that have at least one aspherical surface andare made of a resin material; each of the first lens, the second lens,the third lens, the fourth lens, and the fifth lens is positionedwithout being joined on surfaces facing each other; and the second lenssatisfy a conditional expressions (4) below:−1.50<f2/f<−0.65  (4) where f is the composite focal length of lensesincluded in the entire image pickup lens, and f2 is the focal length ofthe second lens.
 31. The image pickup lens according to claim 30,wherein Abbe numbers of materials used for the first lens and the secondlens satisfy conditional expressions (1) and (2) below:45<ν1<90  (1)22<ν2<35  (2) where ν1 is an Abbe number for d-line of the first lens,and ν2 is an Abbe number for d-line of the second lens.
 32. The imagepickup lens according to claim 30, wherein the second lens has a concavesurface facing the image side on the optical axis.
 33. The image pickuplens according to claim 30, wherein the third lens has a convex surfacefacing the object side on the optical axis and has a meniscus shape. 34.The image pickup lens according to claim 30, wherein an image-sidesurface of the fifth lens has an aspherical shape that contains at leastone inflection point between a center and a periphery of the fifth lens.35. The image pickup lens according to claim 30, wherein the first lenssatisfies a conditional expression (3) below:0.5<f1/f<1.00  (3) where f is a composite focal length of lensesincluded in an entirety of the image pickup lens, f1 is a focal lengthof the first lens.
 36. The image pickup lens according to claim 30,wherein the first lens and the third lens satisfy a conditionalexpression (7) below:−0.15<f1/f3<0.37  (7) where f1 is a focal length of the first lens, andf3 is a focal length of the third lens.